The invention relates to a capacitive sensor array with multiple sensor electrodes, by means of which the penetration of an object into a room is detected in front of the sensor electrodes, and to a control and evaluation device, which is coupled to the sensor electrodes and detects a change in the capacitance of the sensor electrodes in relation to the reference potential.
For example, the U.S. Pat. No. 5,730,165 or respective patent specification DE 196 81 725 B4 discloses a capacitive sensor array with a sensor electrode, by means of which the approach of an object shall be detected, and with a control and evaluation device, which is coupled to the sensor electrode and detects a change in the capacitance of the sensor electrode in relation to mass by coupling the sensor electrode which has a predetermined frequency in periodically repeated fashion with an operating voltage and evaluating at least one parameter of a current or voltage curve which depends on the periodic charging and discharging of the sensor electrode for detecting the capacitance change. At the same time, the parameter of a current or voltage curve depending on periodic charging and discharging of the sensor electrode is a voltage that can be measured via a capacitor, the voltage depending on the charge accumulated on the capacitor, wherein said charge was accumulated in that in periodically repeated fashion the sensor electrode was charged by being coupled to the operating voltage and then discharged via the capacitor by being coupled to the capacitor. Another such capacitive sensor has been disclosed in patent specification EP 1 339 025 B1.
DE 10 2008 063 366 describes a generic device for contact-free actuation of a hatchback of a motor vehicle, which has a first sensor electrode for detecting an object in a first detection range and a second sensor electrode for detecting an object in a second detection range so that the actuation of the hatchback can be activated via the recognition means.
The contact-free actuation of a hatchback can be used, for example, when a person carries items with both hands and a manual actuation of the hatchback is not possible or possible only with difficulty. The object detected by the sensor electrodes can involve a person that approaches the motor vehicle with the intention of actuating the hatchback. At the same time, the actuation of the hatchback describes an opening process, for example, when the person wants to place an item with both hands into the trunk, as well as a closing process of the hatchback when the person has removed an item with both hands from the trunk. The detection includes a body movement, which relates, for example, to the person lifting or swinging the leg or foot in the range of the outer area of the motor vehicle monitored by the sensor array. Disadvantageously, it is possible that a signal for the actuation of the hatchback is triggered even when it does not involve the leg or foot of the particular person. For example, animals can pass the range of the outer area of the motor vehicle monitored by the sensor array, or an object, for example, a ball, can run or roll through the monitored outer area. In addition, it is desired to exclude unclear actuation gestures to increase the detection accuracy.
Therefore, it is desirable to avoid defective function of the hatchback of the motor vehicle.
It is therefore the object of the invention to provide a reliable sensor and evaluation system which reduces the error detection of actuation requirements.